We present a synthesis technique for 3D bandpass frequency selective surface (FSS) with stacked slotline structures. The classical filter synthesis theory is employed to synthesize the frequency responses of the proposed FSS. Then, a second-order Chebyshev bandpass FSS is designed to verify our predictions. A prototype of the designed FSS is in final fabricated and measured, which operates at 3 GHz with a fractional bandwidth of 10%.